This invention relates a method of making an artificial full or partial denture with natural bite and wear properties.
Full and partial artificial dentures are well known to the art. A full or partial denture is defined herein as a removable implantable structure overfitting all or part of the upper gums with some or all teeth removed, or all or part of the lower gums with some or all teeth removed, and providing occlusal surfaces that can be used for chewing in lieu of natural teeth.
It is a longstanding goal of dentists and other professionals involved in denture manufacture to create dentures that, when worn, feel and fit as similar as possible to the patient's natural teeth. To obtain this feel and fit, defined herein as “natural,” it is necessary to create dentures that, when used, result in a resting jaw position, bite pattern, occlusal contact, and relative tooth movement as similar as possible to that of the patient's natural teeth. This will be referred to herein as the patient's “natural bite.” For dentures to maintain a natural bite feel, it is further necessary for artificial teeth within the denture to wear at a rate similar to the wear rate of natural teeth.
The first step in one common method of denture manufacture involves assessment by the dentist of the patient's natural bite or desired bite. Such assessment is typically conducted by measuring the patient's jaw and collecting preliminary impressions of landmark structures in the patient's mouth. These preliminary impressions are used to create a custom impression tray. A denturist or other skilled artisan often makes the custom impression tray. The patient is then fitted with the custom impression tray for more detailed functional impressions of the patient's oral structures, and for assessment of the patient's muscle movements during speech and mastication. The dentist next performs occlusal registration, commonly using wax bite registration, tactile bite registration, intra-oral pin tracing, or gnathometer bite registration techniques. Next, the dentist selects artificial teeth of desired size and shape for attachment to that base. The size and shape of the artificial teeth is selected to most closely replicate the patient's natural or desired bite, as determined by the measurements data collected during the assessment.
The selected artificial teeth are then set in wax try-in base for a test fitting with the patient. Alternatively, the artificial teeth may be removably inserted into a base, such as an acrylic base, intended as the permanent base. The patient provides feedback on the fit and feel of the denture, and the dentist makes any necessary adjustments to the parameters of the base, as well, or optionally alternatively to, the size, shape, and placement of the artificial teeth. Once the patient is satisfied with the look, fit, and feel of the try-in denture, a permanent denture of substantially similar configuration is made by attaching the artificial teeth to a permanent base.
As can be seen, manufacturing dentures to achieve a natural bite feel for the patient is a time and labor intensive process. The manufacture of dentures generally involves an iterative process of test-fitting and reshaping, and involve the time of both a dentist and the time of a skilled denturist or other artisan. A patient may require three, four, five, or even more test-fittings before the denture is satisfactorily shaped and sized.
It is known to the art to increase the precision of the denture manufacture process through the use of computer-aided drawing (CAD) software, often linked to milling, cutting, or other shaping machines capable of forming material in accordance with instructions delivered by CAD software. Such machines will be referred to herein as computer-aided manufacture (CAM) machines. For example, it is known to the art to use a haptic device to allow a computer to create a three-dimensional digital CAD model of a denture based on the patient's oral structures. An actual denture replicating the three-dimensional model can then be made using a CAM machine linked to the CAD program. It is also known to the art for the dentist or denturist to use data collected during assessment to create a three-dimensional CAD model of a denture approximating the patient's oral structure, or containing other desired parameters or characteristics. An actual denture replicating the three-dimensional model can then be made using a CAM machine linked to the CAD program. It is also known to the art for the dentist or denturist to fabricate a denture based on information collected during assessment, and then to create a three-dimensional digital model of that actual denture for record purposes, such as through CAD scanning.
It is known to the art to use CAD models, in conjunction with CAM machines, most notably milling machines, to aid in the precise manufacture of custom denture bases, which often include custom-milled sockets for artificial teeth configured to replicate the natural spacing and placement of the patient's teeth. These sockets can then be fitted with selected commercially available artificial teeth, or with custom manufactured artificial teeth. The patient can then undergo an iterative process of test-fitting, providing feedback, and further alteration of the denture base or teeth to achieve proper occlusion and a satisfactory natural fit and feel.
It is known to use plastic as a material for artificial teeth. Plastic artificial teeth are commonly available, relatively inexpensive, and easy to shape and otherwise work with. Plastic teeth can also be easily made to resemble real teeth. Plastic artificial teeth suffer two notable drawbacks. First, plastic artificial teeth are molded, and thus are not consistently sized. Plastic teeth are commonly made from molds with a long service life. Over the course of the mold's service life, material from the wall of the mold wears away, resulting in an increase in the size of the mold cavity. A plastic tooth made from a mold that has been in service for ten years will therefore commonly be larger than a plastic tooth made from that same mold when the mold was new. Additionally, molds contain multiple cavities, and cavity-to-cavity wear is not necessarily uniform. Thus, while a dentist may select artificial teeth of a certain purported size based on the listed size of the mold, the actual size of the tooth may vary from the listed size specifications, even if the same mold is used over time. This variation and uncertainty increases the likelihood that the denture will not be ideally shaped or sized immediately upon adding the artificial teeth, and increases the likelihood that adjustments will be required. Second, plastic teeth wear at significantly quicker rate than natural biological teeth or teeth restored using porcelain or metal materials. Over time, as the plastic teeth wear more rapidly than natural teeth or other tooth surfaces, any natural bite feel accomplished by the original denture can be altered or lost.
It is known to the art to address the problems posed by the inconsistent sizing and rapid wear of plastic artificial teeth by using metal occlusal inserts. These inserts, however, have poor esthetics and ruin the appearance of real teeth that many patients desire from dentures.
The present invention is directed to a method of denture manufacture that incorporates CAM-formed occlusal inserts made of zirconia. Embodiments of the present method are used to manufacture dentures that are more easily shaped and sized to create a natural bite feel, allow the use of plastic artificial teeth, retain the esthetics of natural teeth, and prevent uneven wear between the artificial teeth and the patient's pre-existing natural or restored teeth. Generally, embodiments of the present invention include a method comprising the steps of:                a. Evaluating a patent to determine desired denture parameters;        b. Fabricating a first denture according to those desired denture parameters, the first denture including at least one occlusal portion;        c. Electronically storing the three-dimensional shape and size of the first denture; d. Forming a holding area within at least one of the occlusal portions of the first denture;        e. Preparing a zirconium occlusal insert for attachment to the holding area, where the occlusal insert is sized and shaped to create a denture approximating the desired denture parameters when mated to the first denture; and        f. Attaching said occlusal insert to said holding area to create a useable second denture, where the second denture approximates said desired denture parameters.        